1. Field of the Invention
This invention relates to an image capture device having an XY address-type image capture element, and in particular to an image capture device capable of detecting flicker due to a commercial power supply, such as through fluorescent lights.
2. Description of the Related Art
In recent years, image capture devices which capture still images, such as digital still cameras, have begun to use XY address-type MOS image capture device, like CMOS image sensors. A CMOS image sensor has a simple structure and can be manufactured at low cost, providing high image quality with low power consumption; but because the timing with which photoelectric conversion is performed is different for each pixel (or more precisely, for each line), when image capture is performed under fluorescent lighting or in some other environment in which the brightness changes periodically, bright-dark horizontal stripes occur in captured images. The horizontal stripes in such captured images is called “flicker”.
In order to suppress this flicker, it has been proposed that the occurrence of flicker be detected, and when flicker is occurring, the exposure time (shutter speed) be controlled according to the flicker frequency. Also, various methods have been proposed for detecting the occurrence of flicker, and also judging the flicker frequency (commercial power supply frequency of 50 Hz or 60 Hz). See for example Japanese Patent Laid-open No. 2003-189129, Japanese Patent Laid-open No. 2002-84466, and Japanese Patent Laid-open No. 2001-119708. Of the above patent references, in Japanese Patent Laid-open No. 2003-189129 the flicker component is extracted from image signals obtained from a CMOS image sensor, the portions with high and low brightness in the flicker component are judged to be “peaks” and “valleys”, and from the number and intervals between the “peaks” and “valleys”, the flicker frequency is estimated. Extraction of the flicker component is performed by taking the difference between the image signals of preceding and succeeding frames to remove image signals of objects contained in the image signals.